Fellow physics major Nelan - who said yes - published a link to a digital copy of the proposal on social news site Reddit this week and it went viral, viewed over 1.7 million times with tens of thousands of Facebook shares and dozens of news articles.

While the proposal actually happened on March 23 last year (their seventh anniversary), she decided to publish it online this week ahead of their wedding (March 23 this year).

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Christie said the pair, both 26, had no idea it would be so popular. "The reaction has been overwhelmingly positive. Lots of comments telling us to go make smart babies, to 'enjoy your entanglement', and lots of congratulations."

McMonigal lured Nelan to the spot where they had met at the University of Sydney, where they both studied advanced maths and physics, saying he needed to show her a paper he was having trouble understanding but had left it at the university.

Nelan said she had a feeling a proposal was brewing but was still "blown away".

"We had been in a date 'war' for a while, as I thought our anniversary was the 23rd [of] May, when we actually started dating, but he thinks it is the 23rd [of] March, when we first met," she said.

"So I knew he would propose on the 23rd [of] March, so he could win the date war."

McMonigal is now doing his PhD on "galactic haloes" in the gravitational astrophysics group at the University of Sydney, while Nelan works as a science communicator in the Questacon Science Squad.

There are dozens of geeky marriage proposals that have gone viral online. Many use modified video games as props, such as the gamer who proposed by spelling out "Lisa Will You Marry Me" in coins in Super Mario World or the guy who harnessed the development team and voice actors from Portal 2 to help create him a custom version of the game for his proposal.

In February last year, Len Kendall harnessed viral media site BuzzFeed to help create and spread a proposal in the form of a meme called "Say Yes Katie".